1. Field of the Invention
This invention relates to a motor vehicle such as an electric vehicle that acquires driving power for running from a high voltage power supply and includes a high voltage system shut-off device that shuts off a high voltage electric system in case of emergency.
2. Description of the Related Art
An electric vehicle acquires driving power for running from a power supply of a considerably higher voltage (several hundred volt) than a battery (usually 12 bolt) installed in a normal motor vehicle. Thus, the electric vehicle is required to take measures to prevent leakage of a high voltage power supply in case of emergency, and accordingly, a variety of techniques have been proposed.
For example, Japanese Laid-Open Utility Model Publication (Kokai) No. 61-202101 has disclosed an electric vehicle that is capable of shutting off the flow of electric current from a power supply to a drive unit upon detection of a collision.
Further, Japanese Laid-Open Patent Publication (Kokai) No. 09-284901 has disclosed the technique of disconnecting batteries from an electric vehicle to prevent leakage of a high voltage, and reconnecting the batteries to the electric vehicle if the vehicle is only slightly damaged.
A sensor for detecting a collision of a vehicle, however, determines whether the vehicle has collided or not according to impact applied to the sensor itself, and therefore, the sensor may determine that the vehicle has collided even in a case where the vehicle has not really collided. In this case, even through the vehicle is able to continue running, the flow of electric current from a power supply is shut off to stop a drive unit for running the vehicle. This disenables the vehicle to run, and therefore, the vehicle stops on the moment.
Moreover, if a sensor for detecting a collision of the vehicle and an electric circuit thereof have failed, the flow of electric current from the power supply to a drive unit is controlled according to false information, and even if the vehicle has not really collided, the flow of electric current from the power supply to the drive may be shut off to disenable the vehicle to run.